The present invention relates to improvements of from cells for the electrolysis of aqueous solutions of alkali metal chlorides and diaphragm cells for the manufacture of chlorine.
The invention relates more particularly to an electrolytic cell comprising, above a base wall, an operating sequence of substantially vertical and parallel anodes and cathodes, enclosed by a peripheral side wall, which rests on the base wall with interposition of a sealing joint.
In cells of this type, the sealing joint opposed between the base wall and the peripheral side wall is strongly acted upon by the large hydrostatic pressure, the high temperature and the very corrosive nature of the electrolyte. It is also subjected to stresses of intense mechanical nature under the effect of the generally very different expansions of the base wall and the peripheral side wall during the operation of the cell.
The joints used heretofore in known cells usually consist of a strip of flexible material, for example of rubber or of mastic on an asphalt base, squeezed under a large pressure between the base wall and the peripheral side wall. In order to obtain sufficient squeezing pressure it is necessary to use joints of small sections or to employ clamping frames. In service, highly compressed joints deteriorate rapidly and rarely ensure effective and lasting sealings. Deterioration of their effectiveness is also accelerated by variations occuring in the conditions of electrolysis. Thus at times local leakage of electrolytes is found to start up following a large and sudden fall in the intensity of the electrolysing current.
A deficiency in sealing of the joint is particularly objectionable in the case of cells where the base wall and the peripheral side wall are both made of metal, since there is a risk that it will lead to the setting up of an intense parasitic electric current between these two walls along the joint.